Oxygen analyzer



L. C.THAYER ETAL f, 2,943,036

OXYGEN ANALYZER June 28, 1960 Filed May 13, 1957 zvsheets-sheet 1 June28, 1960 c. THAYER ETAL 2,943,036

OXYGEN ANALYZER Filed May 13, 195'? 2 vSheets-Sheet 2 J/Z/ra J1.

2,943,036 Patented une Y28, h19.60

OXYGEN ANALYZER Louis C. Thayer, Duarte, and Jan .Haagen-Smit, SouthPasadena, Calif., assignors, by mesue assignments, to BeckmanInstruments, lnc., Fullerton, Calif., a corporation of California FiledMay 13, 1957, Ser. No. 658,547

6 Claims. V(Cl. 204-195) This invention relates to gas analysisequipment and, in particular, to equipment comprising a plurality ofinterconnected cells through which the gas successively passes duringthe anlysis procedure. The unique apparatus described and claimed hereinis suitable for use inconnection with a number of gas analysis processesand is especially adapted for use with processes for determining thepresence of small .quantities of oxygenin other gases. The apparatus ofthe invention will be described as utilized in an oxygen trace analyzer;however, it is understood that the various unique structural featuresdisclosed herein may be used in other gas analysis equipment.

The oxygen analysis process utilizes the well known principle of thegalvanic cell comprising two electrodes coupled by .an electrolyte withat least one of the electrodes, the cathode, positioned so that it mayalso be contacted by the gas being analyzed. In the absence of oxgyen,no reaction occurs in the cell, the cathode not being reactable with theelectrolyte at anytime and the anode being reactable with theelectrolyte only when the electrolyte is reacting with oxygen at thecathode. However, in the presence of oxygen, an electro-chemicalreaction occurs at the cathode and the oxygen is reduced in thisprocess, the anode is partially dissolved and an electrical current isproduced in an external circuit con necting the cathode and anode, themagnitude of the current being a function of the quantity of oxygenpresent in the incoming gas. Y

This process will be described herein in conjunction with a particularanalysis cell; however, it is realized that the process is equallyapplicable to cells utilizing other materials and different combinationsof materials. ln the galvanic cell, an anode, which in this embodimentis of lead, is coupled to a cathode, which is of silvenlby anelectrolyte, which is an aqueous solution of potassium hydroxide. Theelectrodes may be coupled by being immersed in the electrolyte or bybeing separted by a layer of material which is soaked with theelectrolyte. A portion of the cathode is exposed to the sample gas andwhen it contains oxygen, there is an electrochemical reaction `at theinterface of the cathode and the electrolyte involving the oxygen andalso a eraction between the anode and the electrolyte which results inan electrical current in an external circuit coupling the anode andcathode. The reactions occur spontaneously upon closing the circuitexternally, the net result being the consumption of oxygen and thedissolution of the lead electrode. The current generated is proportionalto the partial pressure of oxygen in the gas surrounding the cathode. Inthe complete absence of oxygen, no reactions take place within the celland there is no current produced. Any conventional current indicating orrecording device may be connected to the electrodes to indicate thecurrent generated.

It is preferred that this oxygen analysis process be carried out at asubstantially constant temperature and lat an approximately constant.rate. of ow and pressure, which 2 may be at atmospheric pressre. -Ifsuch constant Achirditions are not maintained, it is necessarytocompensate the readings obtained for the variations, since the currentoutput of the cell is a function of the temperature, rate of flow andpressure as well as of the oxygen content.

It has been found that in the operation of such an analysis cell, thelinearity and long term stability 'of the oxygen content measurementsmay be substantially improved by `utilizing an electrolyte of aparticular conv-V centration. The output of a cell with constantjoxyg'eninput varies with the concentration of the electrolyte, there being avalue of rconcentration at which the output o'f the cell issubstantially constant with small changes in concentration. It has beenfound thatthis concentration of the electrolyte is alsov theconcentration 4'of the electrolyte having the minimum specificresistance. For 'an alkaline electrolyte,V such as potassiumhydroxide,this point also ,corresponds to the concentration providing the maximumconcentration of'ions. For an.aqueous solution of potassiumghydroxide,the optimumV point calls for 27.5 percent potassium hydroxide by weight,corresponding to approximately a 6.2 normal solution. In general, a cellwill desirably be operated with the concentration of the electrolytevarying not more ,than ten percent from the concentration thereof at aminimum specific resistance, i.e., between 24.8 and, 30.2 percentpotassium hydroxide for an aqueous solution thereof.

It has also been found that the linearity and long term stability. ofthe oxygen analysis processy may be sub1- stantially improved ,by theoperation of the analysis cell with a constant concentration for theelectrolyte, preferably, of course, the optimum concentration describedf above. This is achieved by controllingA the vapor pressure of theelectrolyte solvent in the 'sample gas 'entering the analysis cell sothat there is no transfer of solvent between the electrolyte in theanalysis cell and ythe sample gas, thereby maintaining concentration of'the electrolyte constant. In the specific example discussed above, theincoming sample gas is first passed through a container having watertherein and is then.Y passed throughth'e analysis cell. Therelativesizes of the first container and the analysis cell, the 'amount of waterin the first container and the rate of llow of the gas through thecontainer and cell are adjusted so that `the vapor pressure of water inthe sample gas leaving the first container will correspond to theequilibrium walter vapor pressure over the electrolyte in the analysiscell. Under these conditions, water will neither` be added to norsubtracted from the electrolyte in the cell by the sample gasV passingtherethrough. l

In carrying out the sample gas humidifying process described above, itis preferred to use a somewhat diluted solution ofthe electrolyte in thefirst container and to bubble the sample gas therethrough. This providessimple control for the amount of water vapor taken up byY the sample-gas by merely adjusting the concentration of this dilute V.solution ofthe electrolyte relative to the stronger solution of the electrolytecontained in the analysis cell.

The passing of the sample gas through a solution ofthe electrolyte inthe first container also removes undesirable gases from the samplejgas.These gases, such asV carbon dioxide, hydrogen sulfide, acetylene,hydrogen cyanide, sulphur dioxide, nitrogen dioxide and the. like, reactwith the electrolyte and/or electrodes, thereby changing the sensitivityof the cell to oxygen. Y. However, when the sample gas is rfirst passedthrough the same electrolyte in the humidifying container, most of theseundesirable gases are removed, and the cell stability is improved. v

Since the amount of water vapor taken up lby the sample gas passingthrough the first container is a function of the concentration of thesolution in the first container, it

is desirable to maintain this concentration substantially constant. Thisis accomplished by occasionally, such as daily, adding make-up water tothe solution in the container to bring it up to a predetermined level.'Such make-up water should be pure, free of ions and oxygen. The make-upwater is stored in an enclosed container and the sample gas leaving theanalysis cell is owed through this container thereby deoxygenating themake-up water stored therein. At regular intervals or as needed, thedeoxygenated make-up water is transferred to the humidifying container.

'I'his process will continuously and accurately measure the oxygencontent of a sample gas, giving highly accurate results for weeks ofoperation with an output that is linear in the range of zero to severalhundred parts per million of oxygen. vHowever, a number of problems arepresented in the design and construction of apparatus for carrying outthis process. Leaks in the apparatus destroy the accuracy of themeasurements since air containing oxygen enters the sample gas streamthrough the leaks. The leaks will also permit oxygen to enter thedeaerated make-up water prior to its transfer to the humidifier cell.During the operation of the equipment, it is necessary to occasionallyreplace the electrolyte in the various cells and to occasionally replacethe cell structure itself.

Ease of replacement of components and leak-free construction presentconilicting design conditions since these two requirements areordinarily not compatible. Accordingly, itis an object of this inventionto provide a gas analyzer constructed so as to provide the opportunityfor `a minimum of leaks and to provide easy access and maintenance forthe unit. A further object of the invention is to provide such anapparatus having a cell carrier for carrying the cells and providinginterconnections therebetween with cell covers for enclosing the cellsclamped thereto for easy removal.

It is a further object of the invention to provide a gas analysisapparatus having a liquid reservoir on which the cells are carried withthe conduits interconnecting the variouscells passing through thereservoir so that only deaerated make-up water or the relatively oxygenfree sample gas may enter the gasow paths through leaks therein. Anotherobject of the invention is to provide such an apparatus havinginternally positioned valves for .transferring liquid from the reservoirto the humidier cell so that no openings to the surrounding atmosphereare required for valve actuation.

It is another object of the invention to provide gas analysis apparatuswhich may be operated continuously in a vehicle which rolls and pitchesas much as sixty degrecs in any direction without atecting the accuracyof the measurements being performed. A further object of the inventionis to provide gas analysis apparatus in which 'the cells may be rapidlyand easily removed and replaced and in which the electrolyte may bechanged by merely loosening the cell clamps, no pipe line connectionsbeing disturbed.

It is also an object of the invention to provide an analysis cell whichis compact, rugged, inexpensive, longlived and easily and quicklyreplaced. A further object of the invention is to provide such a cellcomprising successive layers of an anode, an absorbent material and aYcathode wrapped around a cell form with the absorbent material havingtabs extending therefrom and adapted to be immersed in a pool of theelectrolyte. Another object vof the invention is to provide such a cellwhich is com.-

pact in shape, being rel-atively short and thick so that all lof theabsorbent material between the electrodes will remain soaked with theelectrolyte during the weeks of operation ofthe apparatus.

Other objects of the invention will more fully appear in the course ofthe following description wherein preferred embodiments are given by wayof illustration or example. Y f

In the drawings:

Fig. 1 is a side view, shown partly in section, of a preferredembodiment of the invention;

Fig. 2 is a sectional view taken along the line 2-2 of Fi 1;

ig. 3 is a sectional view'taken along the line 3 3 of Fig- 1; ,Y

Fig. 4 is an enlarged sectional view of a portion of the apparatus ofFig. 2;

Fig. 5 is a view of a portion of the apparatus of Fig. 1, showing analternative embodiment of the makeup water control valve;

Fig. 6 is anenlargedsectional view of the analysis cell of the apparatusof Fig. l;

Fig. 7 is a sectional view taken along the line 7--7 of Fi 6;

Jig. 8 is an enlarged sectional view of a portion of the apparatus ofFig. 6;

Fig. 9 is a view, shown partly in section and partly diagrammatic, of analternative embodiment of the in vention; y

Fig. 10 is a sectional view taken along the line 10-10 of Fig. 9; and

Fig. 1l is a sectional view of Fig. 9.

i The embodiment of the invention shown in Figs. 1 and 2 includes a duidcontainer or reservoir Z0, a humidiier cell 21, an analysis cell 22, anda ilowmeter cell 23 carried on the fluid container 20. A gas inlet 24, agas outlet 25 and a liquid inlet 26 are provided in the wall of thecontainer 20, each of these openings being adapted to receive a pipeline from a remote position.

The gas outlet 2S and the liquid inlet 26 communicate directly with theinterior of the container 20. The gas inlet 24 is directly coupled toanother opening 29 in the wall of the container 20 by a iluid conduit orpipe 30 positioned within the container 20. Openings 31 and 32 in thewall of the container are coupled by another pipe 33 and openings 34 and35 are connected by a pipe 36. A large threaded opening 39 is providedin the top of the container 20 and is ordinarily stopped by a threadedplug 4t). While not essential to the apparatus of the invention, thisopening provides access to the interior of the container forconstruction and maintenance purposes.

The owmeter cell 23 is clamped to the wall of the container 20 by screws41 with the inlet and outlet of the tlowmeter cell aligned with theopening 35 and an opening 42 in the wall of the container 25,respectively, sealing engagement being provided at these openings byO-rings 43 and 44 positioned in counterbores in the openings 35 and 42,respectively. The iiowmeter may be of any suitable type and preferablyis one in which the gas Hows past two windings of resistance wire whichare connected into an electrical bridge circuit, the difference inresistance of the two windings being an indication of the rate ofV flowof gas past the windings. This type of flowmeter cell is preferredbecause it can be manufactured in a at, compact package for attachmentto a container such as shown herein without requiring any pipes, valvesor the like.

The cells 21 and 22 are held in sealing engagement aken along the line11-11 4against the horizontally disposed lower surface 47 of thecontainer 20 by clamps or bails 48 and 49 respectively, which arepivotally carried on pins 50 projecting from opposite sides of thecontainer 20.

Hollow pins 53 and 54 are fixed in openings 55 and 56 respectively, inthe top of the cell 22 and extend upward therefrom for engagement withcorresponding openings 32 and 34 in the wall of the container 20. Thesehollow pins 53, 54 provide fluid communication with the cell and alsoserve to align the cell with the container when the cell is clampedthereto by the bail 49, O-rings 57 positioned in counterbores in theopenings in the cell providing seals atthe mating surfaces.

escamas t VDetails of the cell clamping arrangement are Shown in Fig. 4,wherein a lock screw 60, preferably made of magnetic material andhavinga threaded shaft- 61 is mounted in that portion of the bail 49 oppositethe-bottorn end 62 of a`cel1 so that the lock screw 60 may be advancedtoward the end 62 by rotating the lock screw relative to the bail. Adisc 63 of permanently magnetized material is positioned in acounterbore 64 in the lock screw 60, the disc being spaced from the lockscrew by ya ball 65 of magnetic material positioned therebetween. Aconical depression 66. is preferably formed in one of the elementsengaging the ball 65 to maintain the ball vin a centered position, thedepression being shown in the disc 63. A pad `67 of felt lor similarmaterial 'is cemented` to the top of the disc 63` to cushion theengagement of the dis'c and the cell end 62. As the lock screwl 60 ismanually rotated, it is advanced upward, bringing the pad intoengagement with the cell as shown in Figs. land 2. The large diameter ofthe lockfscrew provides a long lradius for the force applied thereto,`permitting rapid and leak-free mounting of the cell to the containermanually. The cell may be removed by rotating the `lock screwin theoppositedirection, swinging the bail to one side and lowering the cellfrom the container. After equipment of this nature has been used forawhile, parts may become fouledwith `a dirt and co'rTJrBsion and itoften is diicult to loosen andjremove components. The clamp structuredescribed herein is easily removed in spite "of d irt and corrosionbecause the appara-tus, provides .a long radius and hence, high torquefor the man ually applied force, but provides la very` short radius andhence, low torque for the force tending to hold the structure fixed, itbeing only necessary tob'reak the ball 65 free. The disc 63, beingpermanent-ly magnetized, attracts the ball 65 and lock screw 60 andreduces the likelihood of its loss when a cell is being mounted ordismounted.

In the analysis. cell 2 2, shown in detail in Figs. 6;, 7 and 8, a pool70 of electrolyte is held in the bottom of lahollow cylindrical cover orcontainer 71 ofjglass, or the like for enclosing the cell, the container71 being clamped to Ia cap 72 by the bail 49 with as ealing gasket 73clamped between the cap and container. The cap 72 includes a cylindricalcell form 74 extending downward therefrom terminating above the surfaceof the pool 70. The electrodes of the galvanic cell are mounted on thecell form which is provided with successively increasing externaldiameters for accommodating the material mounted thereon.` A first levelor diameter 75 occupies the major portion of the form 74 and the anodeis mounted thereon. In the preferred embodiment illustrated herein, theanode comprises a sheet 76 of metallic` foil doubled over a wire` 77 andwrapped around the rst diameter '75, Vthe edge of the doubled over sheetcontaining the wire being positioned in Ia groove 80 in the cell form.One end of an electrica-l conductor 81 is connected to the wire 77, theconductor 8 1 passing through and being sealed in an opening 82 in thecap 72 and terminating yat a terminal 33. In an alternativeconstruction, the conductor 81 may be soldered to a tab on the sheet 76which is extended `upward into the opening 82. A layer of absorbentmaterial 84, such as filter paper, Yis wrapped around the ymetallic foilon a second level or -diameter 85 of the vcell form, a plurality of tabs86 being provided on the the cell form 74v outward 'above Vthe pool 70andlthen upward between the inner wall of the container 71 and thewire'turns, leavingthe cell through an opening-96. 5 and the hollow pin54 which connects with the p1pe36.

A quantity of electrolyte ismaintainedin the layer of absorbent material84 between the metallic foilk 76 and the wire 87 by capillary actionthrough the tabs 86 in the pool of electrolyte 70. The foil sheet is theanode and the wireis the cathodefand when thesample gas containingoxygen flows upward past the wire, the reaction previously describedoccurs and theV current generated in the cell may be'measured by anysuitable current measuring device connected to the terminals l83, 92 ormay be used to yactuate a 'control system for controlling the oxygencontent of the sample gas. In itsA preferred embodiment, the metallicfoil of the. cell would be lead, the wire would be silver and theelectrolyte would be aqueous solution of potassium hydroxide `at 'aconcentration of 4approximately 27.5 percent by weight.

In the construction of the analysis cell described above, it ispreferred to make the ow passage between theturns of the cathode and thewall of the container quite'small so that the velocity ofthe sample gasat this point is relatively high resulting in a much-higher sensitivityfor the instrument.-v Furthermore, Vit is preferred that the cell beshort and thick, the diameter of the form preferably being more than one'third the length of Ythe form, so that the` quantityof electrolyte willbe substantially equal throughout thelayer'of absorbent materialpositioned between the electrodes. Y

The humidifier cell 21 includes a cap 99,`a cover or container 100 and agasket '101 similar to Ythose used in the analysis cell 22 and isaligned with and clamped to the huid containerl 20 by means identical tothose of the analysis cell 22. A tube 102 isYV mounted in the cap 99`and extends downward therefrom into thefcontainer 00. The lowerend ofthe/tube being enlarged and terminating in a porous cap `103. A liquid104 including water, preferably a dilute solution of theelectrolyte usedin the Ianalysis cell 22, is placedV in the' container 100 with a levelv'above the porous cap 103 and Vtwo conductors 10S, f106;which aresealed in the wall of the tube 102. The conductors 105', 106 areconnected to terminals 107, 108 (Fig. 3-) by leads 109, 110 passing'upward through the tube 102and outward through the cap 99. Theconductors 105, 106, are used to generate a predetermined quantity ofoxygen in rthe cell by electrolysis` for calibrating the.. instrument,andare preferably made of platinum.

0 Sample 'gas hows into the humidifier cell 21 through the gasv inlet24, the pipe 30, the tube 102, and the porous cap 103, and is bubbledupward through the liquidY 104 and` flows outward to the analysis cellthrough an opening 113 in the cap 99 and thepipe 33. As the gas passesthrough the humidifier cell, itv takes up Water vapor from the liquid104 andV certain gases which may be present -in the sample gas reactwithV the liquid as previousl'y'descnbed. The size of the humidifiercell, the concentration ofthe liquid therein and the rate of how of thesample gas therethrough may be adjusted so that the vapor pressure of'water in the sample gas leaving the humidifier cell corresponds to theequilibrium water vapor pressure over the electrolyte in the analysiscell.

WaterA is transferred from the vcontainer 20 to the humidifier cell 21to make up for the water taken up by the sample gas on passing throughthe humidifier cell, c

this water` transfer being controlled by a valve coupling the containerand humidiher. lpreferred embodiment of a. valve is shown in Fig. 1,this valve being completely enclosed within the apparatus and requiringno openings through which leaks Vmay occur. vmounted within thecontainer 20, being xed in thefwall thereof adjacent the openings 29 and31 and extending downward from; the lower surface 47 engaging an'opening 116 inthe cap 99. VA transverse opening 117 and A valve stem115V isVY an axial opening 118 in the valve s'tem 115 provide uidcommunication between the interior of the container 20 and the interiorof the humidifier 21. Flow through the openings in the valve stem isblocked by a plunger 119 which lits snugly around the stem 115 and restson an O-ring 120 which provides a sealing engagement. A block `121 ofmagnetic material is fixed to the upper end of the plunger 119 and isspaced slightly from the wall of the container 20 when the plunger is inthe down or closed position as shown in Fig. l. Fluid flow occurs fromthe container to the humidifier when an attractive magnetic eld isgenerated above the container moving the block 121 and plunger 119upward until the block engages the wall of the container thus unblockingthe transverse opening 117. Such a magnetic eld may be provided byplacing a magnet 122 on top of the container or by energizing anelectrical coil positioned above the container or by other suitablemeans.

This valve may be operated manually or may be operated automatically,such as by energizing the electrical coil periodically from a clockmechanism or by energizing the electrical coil by a level detectingdevice such as an electric eye circuit or magnetic switch. Analternative embodiment of the valve which provides automatic levelcontrol is shown in Fig. 5. A hollow plug 125 is fixed in the cap 99 andextends downward therefrom providing uid communication from thecontainer 20 to the container `100 through the opening 116 in the cap. Aconical point `126 of a oat 127 engages a downwardly opening, conical.valve seat 128 in the plug 125 for blocking flow of fluid through theplug. lnwardly extending ridges 129 and 130 in the plug 12S guide andlimit vertical movement of the oat. The plug and float are dimensionedso that when the liquid level in the humidier cell is below the desiredlevel the float will move downward with the point 127 out of engagementwith the valve seat 128. When the liquid level raises'to the desiredpoint, the point will engage the valve seat and block further flow ofmakeup water to the humidifier cell.

In the operation of the apparatus, the fluid container 20 is filled withwater through the liquid inlet 26 as required. This water should be pureand free of ions; however, if desired a mixed bed demineralizing resincould be positioned within the container 20 for further purification ofthe water. This water should also be free of oxygen before being addedto the humidifier cell since any oxygen contained therein would disturbthe accuracy of the readings. Deaeration of this water is accomplishedby passing the sample gas through the container after it leaves thetlowmeter cell and before it is exhausted through the gas outlet 25. Asample gas at the desired pressure and ilow rate is introduced into theapparatus at the gas inlet 24, flows through the humidifier` cell 21,then through the analysis cell 22, then through the flowmeter cell 23,through the interior of the container 20 and out through the gas outlet25. All of the pipe connections through which the sample gas llows, withthe exception of the inlet and outlet 24, 25, are positioned within theapparatus so that any leaks occurring merely permit deaerated, deionizedwater or sample gas to enter the system thereby substantiallyeliminating errors inthe measurements due to leakages. Such an apparatusmay be operated in a vehicle which is rolling and pitching as great assixty degrees from the horizontal. The unique method of mounting thevarious cells to the container permtis rapid and easy removal andreplacement of cells and yet is substantially leak-free and rugged.

An alternative embodiment of the apparatus of the invention is shown inFigs. 9, l and l1 and includes a cell carrier 140, a flowmeter cell 141and a liquid reservoir 142. The cell carrier 140 provides a unitarystructure for a humidifier cell 143 and an analysis cell 144 having ainternal ow paths between the cells. A pipe 145 couples the incomingsample gas to the cell carrier,

another pipe 146 conducts the sample gas from the cell" carrier to theowmeter cell, a pipe 147 conducts the sample gas from the owmeter cellto the interior of the reservoir 142 and an overllow pipe 147 providesfor exhaust from the reservoir. Make-up water is fed into the resrvoir142 as required through a control valve 150 and pipe 151. Deaeratedmake-up water is conducted to the cell carrier from the reservoirthrough a pipe t152, ow therein being controlled by a valve 153. Withthis form of construction, the cell carrier may be very compact and maybe mounted separately from the owmeter and liquid reservoir. The make-upwater may be pumped from the reservoir to the cell carrier or thereservoir may be positioned above the c'ell carrier for gravity feed.This embodiment of the invention may also be mounted in a pitching androlling vehicle, the inlet for the overflow pipe 147 being placedsubstantially at the center of the volume of the reservoir so thatsubstantially no liquid is lost therethrough during maneuvering and theexhaust gas pressure is not aected.

The cell carrier 140 includes a central block 156 mounted betweenclamping plates 157, 158 with a cell form 159 extending upwardtherefrom. Space for an annular pool 161 ofelectrolyte is provided atthe junction of the cell form 159 with the central block 156, the outerperipheryof the pool 161 being a cylindrical shell 162 which also servesas an aligning member for a cell cover or container 163. An analysiscell essentially identical to the cell of Fig. 6 is constructed on thecell form 159 and includes a foil sheet wrapped on the form for ananode, a layer of lter paper around the foil and having tabs extendinginto the pool of electrolyte, and a layer of closely spaced turns ofwire as a cathode.

The humidifier cell 143 includes a tube 166 which is a'press t onto aboss 167 extending downward from the Vcentral block 156, the lower endof the tube 166 being closed by a plug 168. A porous disc 169 is clampedbetween the tube and the plug providing a small enclosed space 170between the disc and the plug. A cell cover 171 similar to the cover 163is positioned around the components of the humidifier cell and serves tosupport a pool of diluted electrolyte 172. The cell covers 163 and 171are clamped to the central block 156 by clamp rings 175, 176, gaskets177, 178 and bolts, one of which is shown as 179.

A passage 182 is drilled or otherwise formed in the central block 156 toprovide for gas flow from the pipe 145 through a passage 183 in the tube166 to the base 170. Another passage 184 provides for gas ow from theinterior of the tube 166 to the lower end of the base around theanalysis cell 144. A passage 185 runs downward through the cell form 159and provides communication between the upper end of the analysis celland the pipe 146. The sample gas flows through the various units of theapparatus of Fig. 9 in the same manner as in the apparatus of Figs. land 2. A passage 186 in the central block 156 provides for ow of waterfrom the pipe 152 through the passage 184 into the humidifier cell.

An opening 189 is provided in the wall of the tube 166 near the lowerend thereof and a similar opening 190 is provided in the wall of thetube above the normal level of the electrolyte I1712. When no gas ispassing through the instrument, the level of the liquid within the tube166 will be the same as the level outside of the tube because of theopening 189. However, when a gas is passing upward through the tube 166there is bubbling and foaming within the tube and the liquid level israised above the opening 190 permitting some of the liquid within thetube to ow through the opening 190 into the pool 172. As a result ofthis, liquid also ows from the pool through the opening 189 into theinterior of the tube 166 thereby providing a circulation of electrolyteand equalizing the concentration of the fluid Within and without thetube.

Although exemplary embodiments of the invention have been disclosed anddiscussed, it will be understood that other applications of theinvention are possible and that ythe embodiments disclosed maybe'subjected tovarious changes, modifications andY substitutionswithout'nec- 'of said openings in said wall; a rst iiuid conduitpositioned within said container in engagement with the internal surfaceof said wall. at two of said openings and providing communicationbetween said gas inlet and said lrst cell; a second liuid conduitpositioned within said container in engagement with the internal surfaceof said wall at two of said openings and providing communication betweensaid first cell and said second cell; valve means, including alignedopenings in said wall and said first cell, for providing controlledliquid ow between the interior of said container and said lirst cell;and flow means providing communication between said second cell and theinterior of said container for gas ow through said gas inlet, said firstiiuid conduit, said rst cell, said second fluid conduit, said secondcell, said ilow means, said container and said gas outlet.

2. A gas analyzer as defined in claim l, in which said valve meansincludes a moving element of magnetic material positioned within saidcontainer with at least a portion of 'said element adjacent said wallfor attraction by a magnetic iield generated externally of saidcontainer.

3. A gas analyzer as defined in claim l, in which said valve meansincludes a valve seat and a float positioned in said iirst cell forengaging said valve seat and blocking liquid flow through said alignedopenings.

4. In a gas analyzer, the combination of: a fluid container having aplurality of openings in the wall thereof, including a gas inlet, aliquid inlet and a gas outlet; a iirst cell mounted to the externalsurface of said wall, said iirst cell having openings therein alignedwith and providing communication with certain of said openings in saidwall; a second cell mounted to the external surface of said wall,saidsecond cell having openings thereinVV aligned with and providingcommunication with certain of said openings in said wall; a flowmetercell mounted to the external surface of said wall, said tlowmeter cellhaving two openings therein aligned with and providing communicationwith two of said openings in said wall; a iirst fluid conductorpositioned within said container in engagement with the internal surfaceof said wall at two of said openings and providing communication betweensaid gas inlet and said first cell; a second iiuid conductor positionedwithin said container in engagement with the internal surface of saidwall at two of said openings and providing communication between saidiirst cell and said second cell; a third tluid conductor positionedwithin said container in engagement with the internal .surface of saidwall at two of said openingsl and providing communication between saidsecond cell and one opening of said ilowmeter cell, the other of saidopenings in said iiowmeter cell and said aligned wall opening providingcommunication between said iiowmeter cell and the Y outlet; and -valvemeans, including aligned opemngs in said wall and said rst cell, forproviding controlled liquid iiowV between the interior of said containerand said lir cell.

5. In ya gas analyzer, the combination of `afluidcon tainer having aplurality of'openings in the wall ithereof, including a gas inlet, aliquid inl'etand a gas outlet; a first cell mounted to the'externalsurface of s'aid wall, said first cell having openings therein alignedwith and providing communication with certain of said openings in saidwall, with a pair of said aligned openings providing for liquid flowbetween the interior of said container and said irst cell; a second cellmounted to the external surface of said wall, a second cell havingopenings therein aligned with and providing communication with certainof said openings in said wall; a iirst'fluid conduit positioned withinsaid container in engagement with the internal surface of said wall attwo ofl said openings and providing communication between said gas inletand said rst cell;

a second iiuid conduit positioned within said container in engagementwith the internal surface of said wall at two of `said openings andproviding communication betweenvsaid rst cell and s aid second cell; aplunger movable coaxially with said aligned pair of openings forcontrolling liquid iioW therethrough; a float positioned in said lirstcell and responsive to the liquid level therein for controlling theposition of said plunger as a function of said liquid level; and flowmeans providing communication between said second cell and the interiorof said container for gas iiow through said gas inlet, said first liuidconduit, said first cell, said second iiuid conduit, said second cell,said iiow means, saidcontainer and said gas outlet. Y v.

6. In a gas analyzer, the combination of: a liuid container having aplurality of openings in the wall thereof,

including a gas inlet, a liquid inlet and a gas outlet; a

rst cell for mounting to the external surface of said t Vtherein alignedwith andrproviding communication with certain of said openings in vsaidwall; rst and second cell clamps pivotallyV mounted on said container; alock screw formed of magnetic material threadedly mounted in each ofsaid clamps, with a clamp being movable over the free end of acorresponding cell opposite the end of such cell engaging said containerfor positioning a face of the lock screw opposite `the free end, saidfaceV of said lock screw having a counterbore therein; a permanentmagnet positioned in each of said counterbores; a ball positioned withineach of said counterbores between the lock lscrew and the permanentmagnet, said permanent magnetbeing engageable with said free end ofsaidt cell to urge said cell and container intosealing engagement byrotation of said lock screw; a iirst iiuid conduit positioned withinsaid container in engagement with the' and the interior of saidcontainer for gas flow throughV said gas inlet, said first uid conduit,said first cell, said second fluid conduit, said second cell, said iiowmeans,

said container and said gas outlet.

(References on following page) Y References Cited in the 131e of thispatent UNITED STATES PATENTS Babitch Mar. 12, 1929 Sweeney Dec. 19, 19335 Ornstein Apr. 12, 1938 Bailey Aug. 31. 1948 Fagen r May 16, 1950FOREIGN PATENTS UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. A2,943,036 June 28, 1960 Louis C. Thayer et al.

It is hereby certified that error appears in the-printed specificationof the above numbered patent requiring correction and that the saidLetters Patent should read as corrected below.

Column l, line 57, for "erf-.1ccion" read reaction column 7, line 73,before "internal" strike out "a"l; column lOY line 14,- or,"a second".read said second Sig-ned and sealed this 6th day of December 1960.,

(SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Officer Commissioner ofPatents

1. IN A GAS ANALYZER, THE COMBINATION OF: A FLUID CONTAINER HAVING APLURALITY OF OPENINGS IN THE WALL THEREOF, INCLUDING A GAS INLET, LIQUIDINLET AND A GAS OUTLET, A FIRST CELL MOUNTED TO THE EXTERNAL SURFACE OFSAID WALL, SAID FIRST CELL HAVING OPENINGS THEREIN ALIGNED WITH ANDPROVIDING COMMUNICATION WITH CERTAIN OF SAID OPENINGS IN SAID WALL, ASECOND CELL MOUNTED TO THE EXTERNAL SURFACE OF SAID WALL, SAID SECONDCELL HAVING OPENINGS THEREIN ALIGNED WITH AND PROVIDING COMMUNICATIONWITH CERTAIN OF SAID OPENINGS IN SAID WALL, A FIRST FLUID CONDUITPOSITIONED WITHIN SAID CONTAINER IN ENGAGEMENT WITH THE INTERNAL SURFACEOF SAID WALL AT TWO OF SAID OPENINGS AND PROVIDING COMMUNICATION BETWEENSAID GAS INLET AND SAID FIRST CELL, A SECOND FLUID CONDUIT POSITIONEDWITHIN SAID CONTAINER IN ENGAGEMENT WITH THE INTERNAL SURFACE OF SAIDWALL AT TWO OF SAID OPENINGS AND PROVIDING COMMUNICATION BETWEEN SAIDFIRST CELL AND SAID SECOND CELL, VALVE MEANS, INCLUDING ALIGNED OPENINGSIN SAID WALL AND SAID FIRST CELL, FOR PROVIDING CONTROLLED LIQUID FLOWBETWEEN THE INTERIOR OF SAID CONTAINER AND SAID FIRST CELL, AND FLOWMEANS PROVIDING COMMUNICATION BETWEEN SAID SECOND CELL AND THE INTERIOROF SAID CONTAINER FOR GAS FLOW THROUGH SECOND FLUID CONDUIT, SAID SECONDCELL, SAID FLOW MEANS, SAID CONTAINER AND SAID GAS OUTLET.